| AVS 58th Annual International Symposium and Exhibition | |
| Energy Frontiers Focus Topic | Monday Sessions |
| Session EN+PS-MoM |
| Session: | Plasmas for Photovoltaics & Energy Applications |
| Presenter: | Pierre-Alexandre Delattre, Laboratoire de Physique des Plasmas, France |
| Authors: | P.-A. Delattre, Laboratoire de Physique des Plasmas, France S. Pouliquen, Laboratoire de Physique des Plasmas, France E.V. Johnson, Laboratory of Physics of Interfaces and Thin Films, France J.-P. Booth, Laboratoire de Physique des Plasmas, France |
| Correspondent: | Click to Email |
Voltage Waveform Tailoring (VWT) is a promising new technique for Radio-Frequency (RF) process plasma excitation. It is known that asymmetric waveforms resembling peaks (short positive and long negative voltage) or valleys (long positive, short negative voltage) can produce a voltage self-bias, even in a symmetrical reactor [1], known as the Electrical Asymmetry Effect (EAE). We have implemented a system to provide such voltage waveforms on the RF electrode of our Capacitively Coupled Plasma (CCP) reactor. For a peak to peak voltage (VPP) of 300 V, we can control the self-bias from -190 V to 15 V, without changing any other process parameter. A new differential RF probe gives us the real-time current and voltage derivatives, and therefore, the instantaneous power. For a voltage waveform composed of a 15 MHz fundamental and three harmonics, instantaneous power changes from +1 kW to –1kW in 10 ns. Using a hairpin resonator probe in hydrogen at 13 Pa, we have measured an electron density of 2E8 cm-3 with a standard sine waveform, 2E9 cm-3 with a valleys waveform and 2E10 cm-3 with a peaks waveform (all with VPP= 300V). With a view towards photovoltaic applications, using a gas mixture of 4 % of SiH4 in H2 at 65 Pa, we have achieved a deposition rate of high-quality amorphous silicon of 1 Å/s for sine, 2.7 Å/s for valleys, and 3.8 Å/s for peaks voltage waveforms.
1Brian G Heil et al 2008 J. Phys. D: Appl. Phys. 41 165202